This is first post, I built a dual mono LM3886 with two 300VA transformer and 10000uf/63v cap per rail, the sould is pretty good overall, but everytime when someone mechanical turn on or turn off the light power and sometimes the Refrigerator Compressor also influence , my speaker will have "pia" noise, but this situation not happened for my previous power amp, except this the background is very silence, is anyone experience for this , thanks.
probably RFI interference ( spark gap transmitter)
Do more trouble shooting to discount other connections or gear / music sources.
show us your build for better advice
RF filters on audio input and/or on power entry
shielding enclosure
twisting wires to reduce pick up
Do more trouble shooting to discount other connections or gear / music sources.
show us your build for better advice
RF filters on audio input and/or on power entry
shielding enclosure
twisting wires to reduce pick up
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RF attenuation is required.
Unfortunately National do not show RF attenuation as compulsory in their datasheets and even show example schematic with no RF attenuation for the mains cables nor for the inputs.
Unfortunately National do not show RF attenuation as compulsory in their datasheets and even show example schematic with no RF attenuation for the mains cables nor for the inputs.
Many thanks you guys suggestion, I will try the RF filter at input RCA socket, but any recommend for the value? how about 680 ohm +470pF
The noise may also be coming from your ground. I'm assuming your amp has a safety ground going to the wall outlet. Your refrigerator may be injecting noise into your building's ground wiring, which is finding its way into your amp. Fortunately, there is a rather nice article on this web site which deals with this problem. Here is the link:
http://www.diyaudio.com/forums/diya...udio-component-grounding-interconnection.html
Chapter 2 deals, specifically with the problem of noise.
Good luck!
http://www.diyaudio.com/forums/diya...udio-component-grounding-interconnection.html
Chapter 2 deals, specifically with the problem of noise.
Good luck!
Actually I tried many power amp(none chip), only this Lm3886 have this problem, so I think may be the chip amp is more sensitive for power or environment, next action maybe I will add a regulated power supply(use LT1083), I have no idea is this work?
Don't regulate.
Attenuate the interference.
Fit an RF filter at the input of the chipamp.
Consider adding a filter direct across the RCA input sockets.
Fit mains filter. They are available ready built as IEC sockets with all the correct components inside. Obtain the lowest current rating that will safely power your equipment. They are usually available in 1A, or 3A, or 6A
A metal chassis completely enclosing your amplifier also attenuates interference, especially if you have unattenuated emissions coming from radios and motors around the house.
It is always better to attenuate interference at source. Move the mobile radio, the wireless alarm system, the wireless doorbell, the wireless computer network, etc.
Fit all motors especially and switches in general with a snubbing network. These too are available ready assembled.
Attenuate the interference.
Fit an RF filter at the input of the chipamp.
Consider adding a filter direct across the RCA input sockets.
Fit mains filter. They are available ready built as IEC sockets with all the correct components inside. Obtain the lowest current rating that will safely power your equipment. They are usually available in 1A, or 3A, or 6A
A metal chassis completely enclosing your amplifier also attenuates interference, especially if you have unattenuated emissions coming from radios and motors around the house.
It is always better to attenuate interference at source. Move the mobile radio, the wireless alarm system, the wireless doorbell, the wireless computer network, etc.
Fit all motors especially and switches in general with a snubbing network. These too are available ready assembled.
Thanks all of your comments, I prepared the parts for RC filter will install tonight, I will update the result.
download the data sheet
Look at their example schematic...you'll see that you're missing a cap across the feedback resistor, as well as the cap pointed out by Piggy as missing.
Look at their example schematic...you'll see that you're missing a cap across the feedback resistor, as well as the cap pointed out by Piggy as missing.
more missing
you are also missing the zobel network...your pinging is because the amp is not really stable without the mentioned components.
you are also missing the zobel network...your pinging is because the amp is not really stable without the mentioned components.
I add the 220pf cap across pin9 and pin10 and also add zobel network, seems to hit the problem, the noise is completely gone, but I didn't know which change take effect, anyway thanks all of you provide so many ideas.
Would it be possible to use a higher value than 220pf capacitor? I have the following: 680pF 100Vdc Amtrans AMCH capacitor and 1000pf silver mica in my parts box.
The cap across pins 9, 10 should be 150-220 pF. The values you suggest would impair audio performance.
Also note that to maintain a clean transient/step response, you should add the RC in the feedback path shown in the data sheet (AC Test Circuit #2, if I recall correctly).
A better way to address OP's issue with clicks and pops would be to use an RF filter on the input of the amp. I generally add a few RCs on the input to knock anything above 0.5-1 MHz down considerably. Given the age of this thread, I suspect OP has moved on, though... 🙂
Tom
Also note that to maintain a clean transient/step response, you should add the RC in the feedback path shown in the data sheet (AC Test Circuit #2, if I recall correctly).
A better way to address OP's issue with clicks and pops would be to use an RF filter on the input of the amp. I generally add a few RCs on the input to knock anything above 0.5-1 MHz down considerably. Given the age of this thread, I suspect OP has moved on, though... 🙂
Tom
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Interference can be conducted or radiated.
Conducted through the mains and into the power supply.
Or radiated through the air and into any conductors in its path.
Conducted through the mains and into the power supply.
Or radiated through the air and into any conductors in its path.
Interference can be radiated and/or conducted.
If its radio interference then the amp needs a low pass filter on the input.
If its conducted down the mains then a filter on the power supply will be required.
I have got caught out with lack of power supply spike filtering before.
I unplugged my soldering iron and the spike got into my amp and blew the output transistors. I now always add local 100nf and 100uf capacitors to the amplifier pcb.
If its radio interference then the amp needs a low pass filter on the input.
If its conducted down the mains then a filter on the power supply will be required.
I have got caught out with lack of power supply spike filtering before.
I unplugged my soldering iron and the spike got into my amp and blew the output transistors. I now always add local 100nf and 100uf capacitors to the amplifier pcb.
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